16. Mystery of the Urinal Deuce (Season 10, Episode 09)
The Hardly Boys “skits” (get it, they’re boys, but hardly) are some of the best in South Park history, and for that alone this episode deserves top status. Mackey’s turd jokes are a welcome supplement (mkay).
“Are you saying one fourth of Americans are retards?” -Cartman
“At least one fourth” -Stan [edit 10/15/16: at least two-fifths (40%) according to reported pre-November 2016 polls]
“I got such a raging clue that I almost shot clue glue all over Joe.” -Hardly Boy
“Some pigs never learn.” -George Bush
“[…] laying out a big Fudge Dragon for all to see.” -Mackey